Sarin, a man-made, fast-acting and highly toxic nerve agent, was originally developed in Germany in 1938 to be used as a pesticide. But according to the U.S. Centers for Disease Control and Prevention (CDC), it is far more potent. Sarin can be mixed in liquid to poison drinking water and food, or released as a gas, where it may pose greater risk to a larger number of people.

Victims generally have no idea when they’re being exposed. Sarin is a clear, odorless, colorless and tasteless liquid that evaporates at about the same rate as water when released, making it one of the more volatile nerve agents. It was used in the 1988 Halabja massacre in which Saddam Hussein ordered the release of sarin gas over the Kurdish city and killed at least 5,000 civilians over three days, as well as in a Tokyo subway terrorist attack in 1995 that killed 13 people. Its volatility means sarin is generally mixed just before it’s used and, once made, stored in liquid form. Sarin is also highly corrosive and needs to be stored in specially designed containers that resist breakdown.

Within a few seconds of sarin-gas exposure, victims will start to experience eye pain, drooling, weakness, vomiting, diarrhea and irregular heart rates. Clothing from victims exposed to the gas will continue to release toxic vapors for 30 minutes, causing more people to come into contact with it. For those exposed to the liquid form of sarin, symptoms can occur anytime from a few minutes to 18 hours after consumption. If exposed to a large amount of sarin in either gas or liquid form, victims can experience more severe and painful symptoms such as convulsions, paralysis, loss of respiratory functions and even death.

As with other nerve agents, sarin attacks the nervous system and disrupts the body’s ability to control muscle and gland function. This causes overstimulation of certain metabolic functions — muscles continue to twitch to exhaustion, and breathing revs up to an unmanageable pace — eventually resulting in the loss of all bodily functions. The CDC says even a small drop of liquid sarin on the skin will cause sweating and muscle-twitching on contact.

If only exposed to a small dose, most people can recover. Health officials recommend moving to an outdoor area if exposed indoors, in order to disperse the gas and lower the dose of exposure. Removing contaminated clothing as quickly as possible and washing exposed areas with soap and water can also reduce risk of more severe symptoms. If exposed patients are treated immediately with an antidote that counteracts the toxin in a hospital, the CDC says they will likely survive without neurological problems lasting more than one to two weeks. However, severe and untreated exposure is likely to result in death, making sarin one of the more potent nerve agents.